Corey,

I applaud what you are doing. I'm going through a similar drill myself with the PO170 code. Will try the cleaning route first, but need to order the 5-point torx bit first. Benzworld is fantastic, with amazing, helpful info. I have searched the posts and found much useful info, but I think a current summary will be helpful to many in the future. Thanks.

--Larry C.

 

To be honest... it might be something other than the MAF sensor. I think with the MAF sensor you get 3 code errors.

Usually the P0170 (MAF sensor USUALLY) goes along with code P0136/P0303/P0243/P0300/P0304

See if any of those codes come up. If so, you might need to purchase a NEW maf sensor as opposed to cleaning it. The MAF sensor can only be cleaned 1 or 2 times before needed to be replaced (usually).

 

gakz,

Thanks for the info. I did also get error codes PO301, PO302, and PO303 - misfire detected in cylinders 1, 2, 3. Also PO300 - random/multiple cylinder misfire detected.
Thought this was a separate problem related to spark plugs. I've never cleaned the MAF sensor, and thought that might cure the PO170 problem. Sounds like I may need to spring for a new sensor.

--Larry C.

 

Also code PO410 Secondary Air Injection System came up which I did not find any posts for.

Try searching for P0410, not PO410. It's a zero after the "P", not a capital "O".

 

Since you said you did also receive those codes, get the MAF sensor. It should be less than 200$, DO NOT GET AN EBAY ONE.

That SHOULD solve all of the problems... possibly even the 0410 code, itd be worth it to get the MAF changed out ASAP though to find out.

 

Background

What I have seen is to disconnect the battery while installing. Make sure it remains disconnected for 30 minutes. This will reset all of the computers.

No need to disconnect the battery. It will NOT reset the ME (engine) computer if you disconnect the battery. All engine codes and adaptations are kept in non-volatile memory. The only thing you will reset is your BAS/ESP setup which you will have to resynch afterwards. The SLK is VERY sensitive to disconnecting/connecting the battery and the chances are good you'll end up with a fried instrument panel - search the stickies for descriptions of it.

The best bet is to just buy a cheap scanner to Harborfreigt and reset your codes after swapping the MAF. Alternatively, just start the car afterwards, let it idle for 10 - 15 minutes, then take it out on a GENTLE drive, no hard acceleration or high revving to give the computer a chance to re-adapt to the new MAF. A 10 to 20 mile drive will do the trick.

 

Restating Issue

P0170 Fuel Trim Malfunction (Bank 1), P0410 Secondary Air Injection System, Car will not start just turns over, seems like it is not getting fuel.

Hey Gang,

I checked into the P0410 code more and found the following info from posts on this site.

P0410 Secondary Air Injection System - Look at the cold start air injection system

A check valve under the Air Filter Box allows air to flow into your exhaust, failure of this valve can cause MAF & O2 Sensor problems (Codes I’m getting P0170 and P0410). I have also included a pic of where I believe this valve is located – CheckValve.jpg

- On US models this is used to heat up the O2 sensors and catalyst quickly after a cold start..... the supercharger delivers the air needed....normally-aspirated MB's have an air pump
- A check valve under the Air Filter Box allows air to flow into your exhaust.......failure of this valve can cause MAF & O2 Sensor problems
- A check of the connections to the controller under the front plastic engine cover is also worthwhile
- Valve replacement recommended at 50K miles, apparently these valves can rust through from exhaust heat due to malfunction, then you can get exhaust in the intake before the MAF
- Someone posted that the check valve was a MB recall item due to early failure.

Has anyone done this change with any success? Also does anyone have a part number, official name for this part and recommended provider to purchase from? I checked Auto Parts at AutohausAZ - OEM Auto Parts - Discount Replacement Parts, Resources and Car Care Tips like I did for the MAF and could not find any parts with name similar to check valve.

Autohaus Parts for 1998 Mercedes SLK 230
Search by Car System - Select Car System

Back to the MAF Sensor

I also found more information out about the MAF sensor. You can replace this with two methods. 1) You can replace the Bosch insert only (Pic MAFSensorDetached.jpg) or 2) the whole MAF including the tube. (Pic MAFSensorAttached.jpg)

According to Bazzle’s posts all the Bosch inserts appear to have the same part number. F 00C 2G2 025. Another post suggests MB Part Number on this is PBT-GF30. Make sure you are getting an authentic MB part and not a duplicate.

If you decide to go with only replacing the insert you will need to purchase an Air Mass Sensor Torx Bit to remove it. You can find this and the Mercedes Benz MAF Sensor Insert at the following link Mercedes Benz MAF Sensor Insert.

One post however comments that the only way you can be assured of buying the genuine article is to purchase the entire MAF assembly (not just the insert) from a reputable source, such as autohausaz.com like I listed in my first post on this thread.

Entire MAF Assembly Link
Your Parts Search Returned 1 Part(s)

I still have not found any good steps on how to actually remove and clean or replace the MAF on a SLK 230. I did find some good instructions for SLK 320 thanks to Icdial.

MAF Removal and clean SLK 320 (V6) Thanks to Icdial Picasa Web Albums - Lance - SLK MAF Cleaning

Also here is a good thread about MAF Mass Air Flow Sensor that I got some of my info from. Thanks Bazzle for all of your contributions.
http://www.benzworld.org/forums/r170-slk-class/1244848-maf-ams-afm-etc.html

The following is a site that provides Technical Information on R170 SLK-Class SLK Home Page. I checked it for MAF replacement and part locations but did not have much luck. I found the following schematic on the forums with a part that looks like the complete MAF sensor called B2/5 Hot film mass air flow sensor. Is this the same sensor as the MAF sensor? http://www.benzworld.org/forums/att...ents/r170-slk-class/180640d1212125374-diagnostic-codes-self-adaption-me-sfi.jpg

Thoughts

Should I purchase both the MAF Sensor and Check valve? Try one before the other? I know this is a hit and miss. Anyone else experienced what I went though? Also as I said from my first post please add or correct things I have stated in this thread. I also want this to be a good reference for future users with MAF and Check valve issues. Once I get the solution I will report detailed steps of what I did to fix the error codes of P0170 Fuel Trim Malfunction, (Bank 1) and P0410 Secondary Air Injection System, car turns over and will not start. Like it is being denied fuel.

Thanks for the input.

Cheers
Corey

 

Restating Issue

P0170 Fuel Trim Malfunction (Bank 1), P0410 Secondary Air Injection System, Car will not start just turns over, seems like it is not getting fuel.

Hey Gang,

Should I purchase both the MAF Sensor and Check valve? Try one before the other? I know this is a hit and miss. Anyone else experienced what I went though? Also as I said from my first post please add or correct things I have stated in this thread. I also want this to be a good reference for future users with MAF and Check valve issues. Once I get the solution I will report detailed steps of what I did to fix the error codes of P0170 Fuel Trim Malfunction, (Bank 1) and P0410 Secondary Air Injection System, car turns over and will not start. Like it is being denied fuel.

Thanks for the input.

Cheers
Corey

Hi, Corey.

I can't speak with experience to the MB air injection system, but if the car won't start it isn't the MAF. You can unplug it and the car will still start and run on base settings (heck,unplug it and see if it starts, if it does perhaps you have an unusual short in yours, but that would be very very rare). Fuel trim with the misfire codes tends to suggest it isn't the MAF, from what I understand the air injection system could account for the misfires.

Take care and enjoy the ride,
Greg

 

I get the 0170 code all the time, even if I just bought a new MAF sensor

 

Did you try installing the sensor, or did you just buy it and put on your shelf? You can certainly drive without the MAF sensor plugged in and if you still get P0170 codes then it's probably just a vacuum leak. Actually, in the W203 forum, many P0170 codes are vacuum leaks, not MAF sensors.

 

lmfao that is the one sentence I missed!!! LOL!

Possibly fuel pump then, but i dont know b/c its throwing misfires.

 

I was also getting the P0170 code and P0300 series of misfire codes. No problems starting, no check engine light, but bogs under hard acceleration. Yesterday, I removed the MAF sensor. On my car, the screws holding the insert are T-20 6-point torx with center post. I had this screwdriver bit, so removed the insert. I sprayed the little U-shape wire liberally with CRC MAF Sensor Cleaner (amazingly, available in Palmer, Alaska!). Wiped with Q-tips. As clean as I could make it. Sprayed inside, etc. Today, I drove into Anchorage (about 120 miles round trip) and used the OBD-II reader when I got home. Still had the P0170 code, P0300 codes not showing up.

I guess this means getting a new MAF sensor. My SLK has over 83,000 miles on the original, so I can't complain. Need to decide on just the insert or whole sensor. The housing looks in good shape to me.

Thanks to all for contributions to these posts. I would have never tried this without all of the helpful information.

--Larry C

 

WOW! I was just reading this post, due to my C220 getting the famous P0170 code, and saw PALMER ALASKA!! I grew up in Palmer! Went to Palmer High.. As a matter of fact, my Parents STILL live in Palmer! Small world!:thumbsup:

 

i also have encountered this problem (p170) with some other code i forgot for my slk230. At first, it can't start, called in mechanic from benz for a checked and found out one part go failed (i don't know the name of the part but he said the magnetic of that parts not working so that it won't let the fuel go thru which located at the back of the car juz next to fuel filter). He juz knocked the part twice with a hammer, the car start and straightaway we go to benz service centre to replace the part, fuel filter, MAF( juz clean), oil filter, change oil and reset computer.

After the service, it was good for a week and big problem coming in, the car won't accelerate at normal, it juz slowly pick up the speed, it was very dangerous since there was cars approaching when i make the u-turn. starightaway go back to benz service centre to recheck, p170 pop up from the computer screen, the mechanic juz help me to reset and asked me to come back if problem exist.

after that, the problem come back again and again, after repaired (MAF changed, o2 sensor chenged). the problem still exist. And i heard not only my benz have this problem, other benz in my area oso come with this problem. the problem never solved for few years.

now i get used to it, whenever the engine light come out, i juz reset the computer.

anyone solve this problem let me know. thanks

 

doin12volt,

Enjoyed your post. We moved here 4 years ago after 16 years in Anchorage.

Temperature this morning is 26 below zero (Fahrenheit). Highs today of 10 below to 25 below, without wind chill. Don't think I'll put the top down.

Take care. --Larry C.

 

I have a 1996 e320. I just replaced the MAF with a new, but very cheap aftermarket and cleared the code. After about 20 miles, code 0170 reappeared, and the gas mileage, which was horrible just before the MAF went out (at least I think it went out), is still horrible, probably around 10 mpg or less.

Any thoughts?

 

Steve,
cheap MAF are known to fail quickly, expensive ones as well.
can you get it replaced?

 

Thank you for the help. I ordered the Bosch MAF and will install it. I will let you know what happens.

 

After reading this thread, itmis unclear if anyone actually resolved the issue by replacing the MAF. I have the same issue (bad mileage, bad acceleration, bad performance) Not sure if the MAF is guilty or not!

 

As far as I can tell from many forums and my own frustration with some odd behaviour, the MAF really begins to show signs of failing after oil contamination and just "not working anymore" is rare.

Main culprit for oil contamination is the PCV system. I've only got experience with pre-facelift layout of the engine - I think the facelift models are slightly different - but essentially:

The side on the right looking into the engine bay (exhaust side) is the high-pressure side. There's a centrifugal oil separator that in theory condenses the oil vapour and allows it to run back into the sump, with a minimal amount passing to the intake just because nothing can be 100%. The obvious hoses are very obvious, two smaller hoses run near the exhaust and perish. First is a slightly larger bore hose that takes oil to the dipstick tube. If it's gone, you'll smell oil, might find oil traces.

The second is a 3mm vacuum pipe that goes to the supercharger from the breather on the cam cover. If that one perishes, the oil separator doesn't work correctly. I'm hedging what I'm saying in that I can't remember exactly what it does - I think it provides vacuum, as it also messes with the boost, but am happy to be corrected on that. Either way, it's easily overlooked and gets scorched by heat. I replaced mine with a slightly longer silicone hose routed over the top of the air intake pipe, but simply cable-tying the normal one away from the head/manifold should be sufficient.

On the other side we have the real problem area. The low-load side of the PCV system is the traditional PCV valve with two nozzles screwed into the cylinder head. The rubber pipework can break - it does go brittle and hard over time - but on mine for example, it hadn't broken, was just more rigid than when new. All seals were intact.

The spring loaded valve vents oil vapour into the engine directly, to be burned off. The nozzles, being very narrow bore, get clogged with carbon deposits and crap - particularly when oil is coming in through the intake due to the high-flow oil separator not working. That side failing - so crankcase vapour doesn't relieve pressure into the inlet manifold - seems to increase the pressure on the other side which as it's not at high RPM/lots of flow, just ends up gunged up with oil which gets into the intake.

Upshot of this is, before buying a MAF, check for oil in the intake (mine had a dribble of oil on the air filter, very easy to see), and if there's oil in the intake, clean the easily accessed oil separator and pipework, then prepare for fun & games getting to the PCV valve and pipework which is underneath the inlet manifold. On mine, the PCV valve looks usable but as cleaning the nozzles needs all the pipework removing anyway, I replaced the whole lot.

Ignored for too long things like cam cover gaskets will leak, ending up with problems like oil in the sparkplug pockets. The other telltale on my car was a little trace of oil around the filler cap - and my filler cap is a new one.